Catalytic reforming proces of selective fractions



c. K. DONNELL ET Ax.

cATALYTIc REFORMING PRocEss oF sELEcTlvE FRACTIoNs Filed May 1e, 1955 June 16, 1959 United CATALYTIC REFGRM'ING PROCES 0F SELECTIVE FRACTIONS ApplicationMay 16, 1955, Serial No. 508,384

Claims. (Cl. `20865) This invention relates to the catalytic reforming of straight-run naphthas boiling over the gasoline boiling range and relates more particularly to a combination process in lwhich selected fractions of the naphtha are subjected to reforming under selected conditions, the lower boiling fraction of the naphtha being subjected to` less severe reforming conditions than the higher boiling fraction, and in which a normally liquid low boiling parainic fraction is admixed with the higher boiling fraction prior to reforming.

This application is a continuation in part of our copending application, Serial No. 500,084, iiled April 8, 1955. In that application we disclosed that higher yields of high octane gasoline might be obtained, in reforming a naphtha boiling between 260 F. and 420 F., if the feed, prior to reforming, were diluted with a parainic hydrocarbon boiling below the initial point of the feed, conveniently obtained from the raffinate of anl aromatics recovery process. The present invention makes use of the principles disclosed in` the said co-pending application, but provides a process for the upgrading of a straightrun naphtha, boiling over the' full gasoline boiling range, to a high octane gasoline, without the necessity of including a solvent extraction or other aromatic separation step in the process.

Our invention contemplates fractionating a` straightrun naphtha boiling over the entire gasoline range, say from 90 F. to about 400 F. into three fractions, the first boiling from about 90 F., to about 145 F., the second boiling from about 145 F. to about 210 F., and a third boiling above 210 F. The second fraction is subjected to mild reforming conditions in the presence of a platinum catalyst deposited on an acidic base, and in the presence ofadded hydrogen, in order to isomerize the normal parains contained therein to higher octane number branched chain paratiins, the conditions being selected so that hydrocracking is substantially eliminated and there is a minimum conversion of naphthenes to aromatics. The reformate from this reforming step is fractionated to take overhead an essentially paratinic Vfraction boiling below 160 F., and to recover as bottoms a higher octane gasoline rich in branched chain parains, together with some aromatics and unconverted high octane naphthenes. The first naphtha fraction, the fraction of the iirst reformate boiling below 160 F., and the third naphtha fraction are combined, and the mixture is then subjected to the action of a hydrogenation-dehydrogenation catalyst under severe reforming conditions, in the presence of added hydrogen, Ain order to dehydrocyclize the high boiling parafiins in the feed, to isomerize and dehydrogenate the naphthenes to aromatics, and to isomerize or hydrocrack those higher boiling parans which are not cyclized, to paraiiins of higher octane number. Since the parains boiling below 160 F. are very resistant to dehydrocylization,` and will pass through the reactor virtually unchanged, except for some isomerization or hydrocracking to still lower" boiling paraflins, the paraiinic content of the reaction mixture arent riice will always be high enough so that an equilibrium between aromatics and parans will not be reached, thus insuring a maximum dehydrocylization of the high boiling, low octane, paraflins to the correspondingaromatics of high octane number.

The reformate from this second reforming` stage is distilled to recover an aromatic-rich fraction of very high octane number boiling above 210 F., and: a paratlinic fractionconsisting largely of branched chain paraiins Iboiling below 210 F. The 210 R+ fraction and the 160 F.|- fraction from the. first reformingfstep are blended, and sufficient amountsof` the 210@ F.'- fraction and extraneous butanes` are added to produce a high octane finished gasoline of balanced volatility;

In order that those skilled in the artmaymoreA fully appreciate our invention, and the manner in which it is carried out it will be further described in connection with the accompanying drawing, which. is a diagrammatic flow sheet of the process.

As illustrated inthe drawing, a hydrocarbon feedi boiling from to 400. F.` is introduced through the line 1 to` fractionator 2, in which a fraction boiling from 90 F. to F. is taken overhead. This fraction consists of branched chain hexanes and normal and branched chain pentanes.

A fraction boiling from 145 to 400 F. is taken olf as bottoms from fractionator 2 and is passed` through line 3 to a second fractionator 4 in which a stream: boiling from 145 to 210` F. is removed overhead. This stream, which consists of normal hexane, heptanes, cyclohexane, and methylcyclopentanes is taken through line 5 to reformer 6 in which it is contacted with platinum catalyst deposited on an` acidic base, such` as alumina containing from about 0.31 to 3% combined fluorine. The conditions in reformer 6l are relatively mild, temperature being from about 850 to about 875 F., pressure being from about 3.00 to about 500 p.s.i.g., and preferably in the vicinity of 400 lbs. p.s.i.g., and liquid hourly spacevelocity being about 3. Hydrogen is added to the the feed in such amount that the hydrogen. to hydrocarbon ratio is from about 5 to 1 to` about 10 to l. Under these conditions isomeriz-ation of the straight chain4 paraiins to branched chain paratiins will take place` to a considerable degree. Inaddi-tion a portion of the naphthenes .will be converted to the corresponding aromatics, :while essentially no hydrocracking will take place. Since in the boiling range the naphthenes have about the same octane numbers as the corresponding aromatics, dehydrogenation, with attendant shrinkage in volume, is not desired, and consequently incomplete conversion of the naphthenes is an asset, rather than a liability.

The reaction products are taken from reformer 6 through line 7 and are passed through condenser 8 and thence to separator` 9 in which hydrogenV is removed overhead and recycled to the process through line 10, any excess hydrogen being bled from the system through line 11. The liquid products from separation 9 are taken through line 12, to fractionator 13, in which a fraction boiling below F. is taken overhead, while a high octane gasoline fraction boiling over 160 F. is rmoved as bottoms through line 14 `for blending with other products of the present process.

The 90 to 145 F. overhead fraction from fractionator 2 is taken through line 15 and is blended lwith4 the` 210 to 400 F. fraction removed as bottoms from fractionator 4 through line 16. The fraction boiling below 160 F. taken overhead fromfractionator through line 17 and is mixed with the 210 to 400 F fraction and the 90 to 145 F. fraction. Preferably,r these light paraiiinic fractions will make up at least from 20% to 30% of the mixture, and if the composition of 13` is passed the initial naphtha feed is such that the 90-l45 F. fraction and the 160 F.--fraction together, are insufficient to bring the 'light parafiinic content of the mixture up-to this percentage,asiicient quantity of a paranic fraction boiling under 210 F., obtained from a later stage of the process, may also be added. Similarly, if the 90-145 F. fraction is large enough, the 160 F.- fraction may be omitted from the mixture.

The combined fractions are then passed to reformer 18, in which they are contacted with a bydrogenationdehydrogenation catalyst under relatively severe conditions. The catalystin reformer 18 may be the same catalyst as` is used in reformer 6, but may also be a platinum catalyst depositedV on alumina containing no fluorine or a metal oxide catalystsuch as molybdena or ohromia. -vIf the catalyst contains lluorine, the temperature is preferably from about 900 to 950 F.; while if no iluorine is contained in the catalyst, the temperature should be about 20 degrees higher. In the event a metal oxide catalyst is used, the temperature is preferably from about 950 to 1000 F. The pressure will range from about 500 to about 700 lbs. p.s.i.g. when using a platinum catalyst, or from 100 to 300 p.s.i.g. when using a metal oxide catalyst, theliquid hourly space velocity will be from aboutl to 4 and the hydrogen to hydrocarbon ratio should be from about 3 to 1 to from about 5 to 1. Under these conditions the naphthenes contained in the feed are essentially completely dehydrogenated to the corresponding aromatic, while the high boiling paraflins will be almost completely dehydrocyclized to aromatics, or bydrocracked to lower boiling high octane paraiins. The eflluent from reformer 18 is Vtaken off through line 19 and passed through condenser 20 and thence to separator 21. vHydrogen is taken from separator 21 through line 22 for recycle to the process while excess hydrogen produced in reactor 18 is bled from the system through line 23. Liquid products from separator 21 are passed through line 24 to a fractionator 25, from which a bottoms product boiling above 210 F. is removed through line 26 andpis'blended with the fraction boiling above 160 F. recovered from fractionator 13.

A fraction boiling below 210 F., which is essentially parafinic, is removed from fractionator 2'5 overbead through line 27. A portion of this product may be taken through line 28 and mixed with the below 160 F. fraction in line 17. This will be done, however, only when the combined fractions passing through lines 15 and 17 are less than about 30% of the feed to reformer 18. If these fractions make up about 30% or more of the feed, the entire below 210 F. fraction removed from fractionator 25 through line 27 will be passed through line 29 and condenser 30 to receiver 31. From receiver 31 a portion of the product may be removed through line 32 for blending with the bottoms from fractionators 13 and 25, while another portion of the product may be removed through line 33 for further processing, or for blendingv'with other gasoline fractions, such as a higher boiling catalytically cracked gasoline.

As `may be appreciated from the foregoing, we have invented a process for the upgrading of a straight-run naphtha in which there is minimum degradation of low boiling, high octane naphthenes to aromatics of similar octane` number but smaller volume; in which there is maximum dehydrocyclization of high boiling, low octane paraflins to form aromatics of high octane number; and in which all fractions of a full gasoline boiling rangestraight-run naphtha are utilized to greatest advantage to produce a nal gasoline product of superior octane number in high yield.

. We claim:V

o 1. A reforming process for the upgrading of a straightrun vnaphtha boiling in the full gasolineboiling range which `comprises fractionating a straight-lun naphtha boiling between about 90 F. and about 400 F. into a fraction boiling below about 145 F a fraction boiling between about F. and about 210 F., and a fraction boiling from about 210 F. to about 400 F., contacting the 145 2l0 F. fraction in a iirst reforming zone, in the presence of added hydrogen, with a catalyst comprising platinum, alumina, and fluorine under relatively mild reforming conditions of temperature, pressure, and space rate such that isomerization of paraflins is promoted and dehydrogenation of naphthenes and hy drocracking is minimized; recovering a first reformate, fractionating the first reformate, recovering a paraiflnic fraction boiling below about F. and a fraction of enhanced octane number boiling above about 160 F.; mixing the naphtha fraction boiling below about 145 F., the naphtha fraction boiling from about 210 F. to about 400 F., and the fraction of the first reformate boiling below about 160 F., contacting the mixture in a second reforming zone, in the presence of added hydrogen, with a hydrogenation-dehydrogenation catalyst under relatively severe reforming conditions of temperature, pressure, and space rate such that dehydrocyclization and hydrocracking of Ca-lparains and dehydrogenation of naphthenes is promoted, and fractionating the effluent from the second reforming zone to recover a paraflinic fraction boiling below about 210 F., and an aromaticcontaining fraction boiling above about 210 F.

2. A gasoline reforming process which comprises fractionating a straight-run naphtha boiling in the full gasoline boiling range into a paraliinic fraction boiling below about 145 F., a fraction boiling between about 145 F. and about 210 F., and a fraction boiling above about 210 F.; contacting the 145 210 F. fraction in a first reforming zone, in the presence of added hydrogen, with a catalyst comprising platinum, alumina, and iluorine, at a temperature of from about 850 F. to about 875 F., and at a pressure of from about 300 to about 500 p.s.i.g.; recovering a first reformate, fractionating the first reformate to recover a paraflinic fraction boiling below about 160 F. and a fraction of enhanced octane number boiling above about 160 F.; mixing the naphtha fraction boiling above 210 F. with at least `a part of the fraction boiling below about 145 F. and with the lirst reformate fraction boiling below about 160 F.; contacting the mixture, in a second reforming zone, in the presence of added hydrogen, with a hydrogenation-delhydrogenation catalyst, at a temperature of from about 900 to about l000 F. and at a pressure of from about 500 p.s.i.g. to about 700 p.s.i.g.; and recovering a second reformate of enhanced octane number; and blending the fraction of the rst reformate boiling above about 160 F. with the second reformate.

3. A gasoline reforming process which comprises fractionating a straightrun naphtha boiling in the full gasoline boiling range into a parainic fraction boiling below about 145 F., a fraction boiling between about 145 F. and about 210 F., and a fraction boiling above about 210 F.; contacting the 145-2l0 F. fraction in a rst reforming zone, in the presence of added hydrogen, with a catalyst comprising platinum, alumina, and fluorine, under isomerizing conditions of temperature and pressure, recovering a rst reformate, fractionating the first reformate to recover a parainic fraction boiling below about 160 F., and a fraction of enhanced octane number boiling above 160 F., blending, with Vthe naphtha fraction boiling above 210 F., a lower boiling parainic fraction selected from the naphtha fraction boiling below 145 F., and admixtures thereof with the'flrst reformate fraction boiling below about 160 F., and thehereinafter specified parainic fraction boiling below 210 F., in such proportions that at least 20% of the blend will boil below 210 F., contacting the blend in a second reforming zone, in the presence of added hydrogen, with a hydrogenation-dehydrogenation catalyst under dehydrocyclization conditions of temperature and pressure,

. recovering a second reformate, and fractionating the second reformate to recover said paraflinic fraction boiling below about 210 F., and a fraction rich in aromatics boiling above about 210 F.; and blending the fraction of the rst reformate boiling above about 160 F. with the fraction of the second reformate boiling above about 210 E. and with a suicient quantity of the fraction of the second reformate boiling below 210 F. to yield a gasoline of balanced volatility.

4. The process according to claim 3 in which the temperature in the first reforming zone is from about 850 F. to about 875 F., and in which the temperature in the second reforming zone is from about 900 F. to about 1000" F.

5. The process according to claim 4 in which the pressure in the first reforming zone is from about 300 to about 500 p.s.i.g., and in which the pressure in the 15 second reforming zone is from about 500 p.s.i.g. to about 700 p.s.i.g.

6 References Cited in the ile of this patent UNITED STATES PATENTS 2,337,601 Hays Dee. 28, 1943 2,372,711 Cornforth Apr. 3, 1945 2,651,597 Corner et al Sept. 8, 1953 2,736,684 Tarnpoll Feb. 28, 1956 FOREIGN PATENTS 720,388 Great Britain Dec. 15, 1954 OTHER REFERENCES Brooks et al.: The Chemistry of Petroleum Hydrocarbons (1955), vol. III, page 41, article by Pines et al., Reinhold Publishing Corp., New York publishers. 

3. A GASOLINE REFORMING PROCESS WHICH COMPRISES FRACTIONATING A STRAIGHT-RUN NAPHTHA BOILING IN THE FULL GASOLINE BOILING RANGE INTO A PARAFFINIC FRACTION BOILING BELOW ABOUT 145*F., A FRACTION BOILING BETWEEN ABOUT 145* F. AND ABOUT 210*F., AND A FRACTION BOILING ABOVE ABOUT 210*F., CONTACTING THE 145-210*F. FRACTION IN A FIRST REFORMING ZONE, IN THE PRESENCE OF ADDED HYDROGEN, WITH A CATALYST COMPRISING PLATINUM, ALUMINA, AND FLUORINE, UNDER ISOMERIZING CONDITIONS OF TEMPERATURE AND PRESSURE, RECOVERING A FIRST REFORMATE, FRACTIONATING THE FIRST REFORMATE TO RECOVER A PARAFFINIC FRACTION BOILING BELOW ABOUT 160*F., AND A FRACTION OF ENHANCED OCTANE NUMBER BOILING ABOVE 160*C., BLENDING, WITH THE NAPHTHA FRACTION BOILING ABOVE 210*F., A LOWER BOILING PARAFFINIC FRACTION SELECTED FROM THE NAPHTHA FRACTION BOILING BELOW 145*F., AND ADMIXTURES THEREOF WITH THE FIRST REFORMATE FRACTION BOILING BELOW ABOUT 160*F., AND THE HEREINAFTER SPECIFIED PARAFFINIC FRACTION BOILING BELOW 210*F., IN SUCH PROPORTIONS THAT AT LEAST 20% OF THE BLEND WILL BOIL BELOW 210*F., CONTACTING THE BLEND IN A SECOND REFORMING ZONE, IN THE PRESENCE OF ADDED HYDROGEN, WITH A HYDROGENATION-DEHYDROGENATION CATALYST UNDER DEHY- 